Excluding municipal lighting, they tried cutting back once by turning off the road lights at 2AM (or thereabout). The result was a spike in traffic crashes during the unlit hours so the experiment was canceled.

It seems they do shut some off again between midnight and 6AM since 2011.

The problem is mostly confined to Flanders. South of Brussels, things are more rural. One of the issues is that they want to keep the on/off ramps and other dangerous areas lit, yet at the same time, the policy excludes sections of less than 2 miles from being shut off to avoid "strobe fatigue". Population distribution being what it is, that means half the roads remain lit.

Once used to "all lit, all the time", it is surprisingly hard to break the habit. Doing 65 in darkness definitely fell into the "WTF" category once I started spending more time in the US. I can't see anyone in the current crop of politicos having the spine to stand up to the popular revolt sure to ensue if they were to shut more lights off.